Treatment of polyphenyl thioethers with alkali metal hydrides



United States Patent 3,518,314 TREATMENT (PF POLYPHENYL TI-IIOETHERS WITH ALKALI METAL HYDRIDES Carl W. Gieseking, St. Louis, Mo., assignor to Monsanto Company, St. Louis, Mo., a corporation of Delaware No Drawing. Filed Apr. 1, 1968, Ser. No. 717,982 Int. Cl. C07c 149/02 US. Cl. 260-609 14 Claims ABSTRACT OF THE DISCLOSURE A process for the treatment of polyphenyl thioethers to improve their oxidative stability and to decrease their corrosiveness to metals wherein the thioether is contacted with a contacting agent selected from the group consisting of alkali metal aluminum hydrides and alkali metal hydrides.

This invention relates to the treatment of certain polyphenyl thioethers which can also be classed as polyphenyl sulfides, which term is meant to include polyphenyl sulfides in which one or more, but not all of the sulfur atoms have been replaced with oxygen atoms, to improve their oxidative stability and to decrease their corrosiveness to metals.

Because of the wide variety of applications under which functional fluids are utilized, a concurrence of many properties, both physical and chemical, are needed in a particular fluid to provide the service demanded. One of the most rigorous demands on fluids is made by gas turbine aircraft hydraulic systems and gas turbine engine lubrication systems. As the speed and altitude of operation of jet powered aircraft increases, lubrication problems also increase because of higher operating temperatures and higher bearing pressures resulting from the increased thrust needed to obtain higher speeds and altitudes. As the service conditions encountered become increasingly severe, the useful life of the functional fluid is, of course, shortened.

The useful life of any lubricant or hydraulic fluid can be adjudged on the basis of many criteria such as the extent of viscosity increase, the extent of corrosion to metal surfaces in contact with the lubricant and the extent of engine deposits. Those skilled in the art have found various ways to improve lubricants and to thus retard or prevent the effects which shorten the useful life of a lubricant. Thus, for example, small amounts of other materials, or additives, can be added to lubricants in order to affect one or more-of the properties, of the base lubricant. Oftentimes, however, it is diflicult, especially as operating temperatures are increased, to find additives which will still perform the function for which they are added and yet not inject other problems.

Polyphenyl thioethers have been proposed as compounds which can be employed as functional fluids in many different types of application, such as hydraulic fluids, damping fluids, synthetic lubricants, particularly useful as gas turbine lubricants, and atomic reactor coolants.

It has now been found that the oxidative stability and thus the useful life of polyphenyl thioethers can be greatly extended, even under the severe conditions encountered in jet engines and other devices operating at temperatures of the order of 500 F. and higher, by contacting such thioethers in the liquid phase with a contacting agent selected from the group consisting of (1) alkali metal aluminum hydrides, (2) alkali metal hydrides and (3) mixtures of (l) and (2) at a temperature above about 50 C. Also, by the process of this invention, the corrosiveness toward certain metals of such thioethers is significantly reduced.

3,518,314 Patented June 30, i970 It is, therefore, an object of this invention to provide a method for increasing the oxidation resistance of polyphenyl thioethers and compositions thereof. Another object is to provide polyphenyl thioethers and compositions thereof which have decreased metal attack and give decreased formation of engine deposits.

As used herein the term polyphenyl thioether includes a compound or physical mixture of compounds represented by the formula:

l/ l l a l Ll ts wherein A, A A and A are each a chalkogen having an atomic number of 8 to 16, provided at least one of A, A A and A has an atomic number of 16, X, X X X and X each are selected from the group consisting of hydrogen, alkyl, haloalkyl, halogen, arylalkyl and substituted arylalkyl, L, m and n are whole numbers each having a value of from 0 to 8 and a is a Whole number having a value of from 0 to 1 provided that when a is 0, m is a whole number having a value of from 1 to 2. Typical examples of such polyphenyl thioethers are:

where m is a Whole number from 0 to 6,

can

where A and A are each selected from oxygen and sulfur,

where x and y are whole numbers from 0 to 3 and the sum of x-l-y, is from 1 to 6 and A and A are each selected from oxygen and sulfur but at least one of A and A is sulfur.

Specific examples of polyphenyl thioethers are:

Bis m-phenylmercaptophenyl) sulfide 1,2,3-tris phenylmercapto) benzene 1-phenylmercapto-2,3 -bis (phenoxy) benzene 1,3-phenylmercapto--phenoxybenzene 1,2,4-tri s( phenylmercapto benzene 1,3,5 -tris (phenylmercapto benzene o-Bis (o-phenylmercaptophenylmercapto benzene p-Bis (p-phenylmercaptophenylmercapto benzene p-Bis(o-phenylmercaptophenylmercapto) benzene p-Bis (m-phenylmercaptophenylmercapto benzene m-Bis (p-phenylmercaptophenylmercapto benzene O-bis (p-phenylmercaptophenylmercapto benzene ar-Bis (phenylmercapto) ar'- (phenylmercapto benzene 2,2'-bis(phenylmercapto) diphenyl ether 2,3'-bis (phenylmercapto) diphenyl ether 2,4'-bis (phenylmercapto diphenyl ether 4,4'-bis (m-tolylmercapto diphenyl ether 3,3 -bis (m-tolylmercapto diphenyl ether 2,4-bis (m-tolylmercapto diphenyl ether 3,4'-bis (m-tolylmercapto diphenyl ether 3,3 -bis (p-tolylmercapto diphenyl ether 3,3 -bis (xylylmercapto diphenyl ether 4,4-bis (xylylmercapto) diphenyl ether 3,4'-bis (xylylmercapto diphenyl ether 3 ,4-bis (m-isopropylphenylmercapto) diphenyl ether 3,3-bis (rn-isopropylphenylmercapto) diphenyl ether 2,4'-bis (m-isopropylphenylmercapto diphenyl ether 3,4-bis(p-tert.-butylphenylmercapto)diphenyl ether 4,4-bis (p-tert.-butylphenylmercapto diphenyl ether 3,3 -bis (p-tert.-butylphenylmercapto diphenyl ether 3,3 -bis (m-di-tert.-butylphenylmercapto diphenyl ether 3,3 -bis (m-chlorophenylmercapto) diphenyl ether 4,4-bis (m-chlorophenylmercapto diphenyl ether 3, 3 -bis (m-trifluoromethylphenylmercapto) diphenyl ether 4,4-bis (m-trifluoromethylphenylmercapto) diphenyl ether 3 ,4'-bis (m-trifiuoromethylphenylmercapto) diphenyl ether 2, 3 '-bis (m-trifluoromethylphenylmercap to) diphenyl ether 3,3 -bis (p-trifluoromethylphenylmercapto diphenyl ether 3,3'-bis (o-trifluoromethylphenylmercapto) diphenyl ether 3,3'-bis (m-methoxyphenylmercapto diphenyl ether 3,4'-bis (m-isopropoxyphenylmercapto) diphenyl ether 3,4'-bis (m-perfiuorobutylphenylmercapto) diphenyl ether 2-m-tolyloxy-2-phenylmercaptodiphenyl sulfide 2-p-tolyoxy-3'-phenylmercaptodiphenyl sulfide 2-o-tolyloxy-4'-phenylmercaptodiphenyl sulfide 3-m-t0lyloxy-3'-phenylmercaptodiphenyl sulfide 3-m-t0lyloxy-4'-phenylmercaptodiphenyl sulfide 4-m-tolyloxy-4'-phenylmercaptodiphenyl sulfide 3-xyly1oxy-4'-phenylmercaptodiphenyl sulfide 3-xylyloxy-3'-phenylmercaptodiphenyl sulfide 3-phenoxy-3-m-tolylmercaptodiphenyl sulfide 3-phenoxy-4-m-tolylmercaptodiphenyl sulfide 2-phenoxy-3-p-tolylmercaptodiphenyl sulfide 3-phenoxy-4-m-isopropylphenylmercaptodiphenyl sulfide 3-phenoxy-3-m-isopropylphenylmercaptodiphenyl sulfide 3-m-tolyoxy-3-m-isopropylphenylmercaptodiphenyl sulfide 4-m-trifluoromethylpheonxy-4-phenylmercaptodiphenyl sulfide 3-m-trifluoromethylphenoxy-4-pheny1mercaptodiphenyl sulfide Z-m-trifluoromethylphenoxy-4-phenylmercaptodiphenyl sulfide 3-m-trifiuoromethylphenoxy-3'-phenylmercaptodiphenyl sulfide 3-p-chlorophenoxy-3-phenylmercaptodiphenyl sulfide and 3-m-bromophenoxy-4'-phenylmercaptodiphenyl sulfide Mixtures of polyphenyl thioethers can also be treated according to the method of this invention. A typical example of a mixture of polyphenyl thioethers is one which contains by weight from about 45% to about 55% m-phenoxyphenyl-m-phenylmercaptophenyl sulfide, from about 25% to about 35% bis(m-phenylmercaptophenyl) sulfide and from about 18% to about 25% bis(m-phenoxyphenyl) sulfide.

Preferred polyvinyl thioethers of this invention are mixtures comprising m-bis(phenylmercapto)benzene and certain other materials which have properties that make them well suited for the uses disclosed above and particularly those applications, such as jet engine lubricants, requiring thermal and oxidative stability and wide liquid range.

Such other materials can advantageously be employed in amounts of from about 20 to about 200 parts by weight per parts of m-bis(phenylmercapto) benzene. The other materials contemplated to be used with mbis(phenylmercapto) benzene to provide such preferred mixtures are as follows:

(a) The three-, four-, fiveand six-ring polyphenyl thioethers, for example o-bis(phenylmercapto) benzene bis(m-phenylmercaptophenyl) sulfide Q U U O m-phenylmercaptophenyl-p-phenylmercaptophenyl sulfide (T TTO the trisphenylmercaptobenzenes (VIII) such as 1,2,4-trisphenylmercaptobenzene, 3,3'- bis(phenylmercapto)biphenyl m-bis(p-phenylmercaptophenylmercapto) benzene (XII) Q' U 'U U U O (b) The mixed polyphenyl oxy-thioethers having the formula:

RY-(R Y cR XIII 3, 3 '-bis (phenylmercapto diphenyl ether 3,3 -bis (phenoxy) diphenyl sulfide 3-phenoxy-3'-phenylmercaptodiphenyl sulfide 3-phenylmercapto-3'-phenoxydiphenyl ether 3,4-b is (phenylmercapto) diphenyl ether c n-an m-bis (m-phenylmercaptophenoxy )benzene and 3-phenylmercapto-3'-(m-phenylmercaptophenylmercapto) diphenyl ether (c) The four-, fiveand six-ring polyphenyl ethers which can be represented by the structure where m is 2, 3, or 4 such as bis(m-phenylyphenyl)ether, m-phenoxyphenyl p-phenoxyphenyl ether, m-bis(mphenoxyphenoxy)benzene, m- (m-phenoxyphenoxy) (pphenoxyphenoxy) ]benzene, p- [p-phenoxyphenoxy) (m- (XXI) phenoxyphenoxy)]benzene, p-bis (m-phenoxyphenoxy) benzene, m bis(p phenoxyphenoxy)benzene and 0- bis (m-phenoxyphenoxy)benzene and combinations of (a) through (c). Compounds of (a) and (b) above are also contemplated to be employed alone or in combination with each other and (c) in the process of this invention.

Of the various possible mixtures described above, certain more limited compositions are preferred because of wider liquid range and in many cases unexpectedly low evaporation losses as well as other properties which make such compositions well suited for lubricants for jet engines. The more limited, preferred compositions above referred to are listed in Table I below.

TABLE I Percent by N 0. Components wt. range 1 m-Bis (phenylmereapto) benzene -70 A mixture of about 65% m-bis (m-phenoxyphenoxy) benzene, 30% m-[(m-phenoxyphenoxy) (p-phenoxyphenoxyflbenzene, 5% m-bis(p-pl1enoxy phenoxy)benzene. 20-30 2 m-bis(phenylmereapto)benzene. 55-45 m-bis(phenoxy)diphenyl sulfide 45-55 3 m-bis(phenylmercapto)benzene. 65-35 3-phenoxy-3-phenylmercapt0diphenyl sulfide. 35455 4 m-bis(phenylmereapto)benzene 99-15 m-bis(phenylmercaptophenyl)sulfide 1-31 m-bis(phenoxy)diphenyl sulfide 1-65 5 mbis(phenylmercapto)benzene 99-12 bis(nl-phenylmereaptophenyl)sulfide H31 3-phenoxy-3-phenylmercaptodiphenyl sulfide 1-73 6 m-bis(phenylmercapto)benzene 48-1 Bis (rn-phenylmercaptophenyl)sulfide. 1-12 m-B is(phenylmercaptophenyl) ether 48-98 7 m-Bis(phenylmercapto)benzene 08-25 Bis (m-phenylmereaptophenyl)sulfide 1-31 m-Phenylmereaptophenyl-p-phenylmercaptophenyl sulfide M 1-65 8 m-Bis(phenylmercaptc)benzen 98-1 m-phenoxy diphenyl ether 1-80 o-Bis(phenylmercapto)benzene 1-54 9 m-Bis(phenylmercapto)benzene 9042 A mixture comprising, by weight 20-35% blS(I1l phen ylrnercaptophenyl)sulfide, 4060% 3phenoxy 3-phenylmercaptodiphenyl sulfide, 20-30% bis(mphenoxyphenyDsulfide. 1-58 The contacting agents employed in the process of this invention are alkali metal aluminum hydrides and alkali metal hydrides. The most commonly available contacting agents contain either lithium, sodium or potassium. The preferred aluminum hydride is lithium aluminum hydride while the preferred hydride is potassium hydride. Other contacting agents are sodium aluminum hydride and potassium aluminum hydride, lithium hydride and sodium hydride. The contacting agent is generally added as a solid in particulate form.

In carrying out the process of this invention improved polyphenyl thioethers are prepared by contacting such thioethers by means known to the art for contacting liquids with solids, e.g., by agitating a mixture of the fluid and the solid particles or by passing the fluid through a packed column of the solid particles. The process of this invention may be operated above the melting point of the contacting agents and in such event improved polyphenyl thioethers are prepared by contacting such thioether by means known to the art for contacting liquids with liquids. Preferably an inert atmosphere such as nitrogen or carbon dioxide is provided over the surface of the liquid in the treatment vessel. The fluid can be recovered after treatment by means known to the art for separating liquids from solids as by filtration or by distilling the liquid from the treatment vessel under reduced pressure.

Generally the improvements obtained by the process of this invention are unaffected by the concentration of the contacting agent and the time of contact; however, it should be realized that there are minimum values of concentration and time below which the process of this invention becomes impractical. A minimum concentration of contacting agent of about 0.01% by weight of polyphenyl thioether to be treated should be used. The

length of time of contact will vary depending upon variances in temperature and the concentration of the The corrosiveness to metals was determined by weighing metal specimens of known size before and after the test.

TABLE II Treating agent Percent concentration, viscosity Metal attack, mg./cm. Temperature, Treating percent; increase ExampleNo. Time, hrs. 0. agent by weight at 100 F. Cu Ag eat 0. 9 5. 69 2. 70 LiAlHt 1 4. 5 4. 45 2. LiAlH4 0. 5. 0 4. 86 2. 03 LlAlIIl 0.5 1.8 -l. 08 O. 62 NaH 1 1. 0 2. 47 l. 08

contacting agent but a minimum time of about one hour at about 50 C. should be used. In general, times in the order of 1 to 48 hours are sufficient for most conditions.

The temperature at which the process of this invention is carried out is above about 50 C. and generally from about 100 C. to about 350 C. or higher. The choice of a particular temperature will be dictated, for example, by time available, by the facilities available, the concentration of the contacting agent and the characteristics of the fluid being treated. For example, when using the contacting agent in amounts of from 0.5 to 1% by weight of the fluid a contact period of from about 1 to 5 hours at temperatures in the range of about 100 C. to about 300 C. provide the optimum efiiciency of equipment and benefit to the fluid.

The mechanism through which the improvements in the properties of the esters treated according to the method of this invention occurs is not completely understood at this time. Particularly unexpected is the improvement in the oxidative stability of the above-described fluids brought about by the process of this invention.

The following non-limiting examples illustrate the process of this invention.

Separate samples of m-bis(phenylmercapto) benzene, were treated by contacting them with contacting agents of this invention. The polyphenyl thioether and the contacting agent were introduced into a treating vessel and covered with a nitrogen atmosphere. The contents of the vessel were agitated for a period. of time and at a temperature as indicated in Table II below. The contacting agent was separated from the polyphenyl thioether by filtration. The treated fluid was then subjected to a recognized bench test to determine its oxidative stability and corrosiveness to metal. The results of the treatments are reported below in Table II.

The data reported in Table II was obtained by employing one of the major bench scale methods used for evaluating oxidative stability. The procedure is described in Federal Test Specification 791, Method 5308, excepting that the fluid to be tested is heated to a temperature of 500 F. for a period of 48 hours instead of 250 F. for 168 hours in the presence of certain metals and air. The viscosity increase of the fluid is determined. Additionally, information as to the corrosiveness of a fluid to metals can also be obtained. In order to demonstrate the eifectiveness of the process of this invention in improving the oxidative stability and reduced corrosiveness of the fluids, samples of the fluid treated as described above and on an untreated sample of the same fluid was tested. The metal specimens used were steel, copper, silver, titanium, magnesium alloy and aluminum alloy. However, only the results upon copper and silver are reported since the untreated fluid tested had essentially no effect on steel, magnesium alloy, titanium and aluminum alloy. Viscosity measurements were made according to ASTM Method D44553T using a Cannon-Finske modi fied Ostwald viscosimeter. The percent viscosity increase was determined by measuring the viscosity of the samples before and after the test, dividing the difference by the original viscosity and multiplying the quotient by 100.

According to the data in Table II above the reduction in viscosity increase indicates the increased oxidative stability of polyphenyl thioether brought about by contacting such thioethers with contacting agents of this invention. In addition the corrosiveness to copper and silver were greatly reduced. Thus the useful life of the polyphenyl thioethers as functional fluids is increased when such thioethers are treated according to the process of this invention.

While this invention has been described with respect to various specific examples and embodiments, it is understood that the invention is not limited to such examples and embodiments and that it can be variously practiced within the scope of the following claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A process to improve the oxidation stability and decrease corrosiveness to metals of a polyphenyl thioether which comprises contacting a polyphenyl thioether with at least 0.01 percent by weight of the polyphenyl thioether of a contacting agent selected from the group consisting of (1) alkali metal aluminum hydrides (2) alkali metal hydrides and (3) mixtures thereof at a temperature from about 50 C. to 350 C.

2. The process of claim 1 wherein the contacting agent is an alkali metal aluminum hydride.

3. The process of claim 2 wherein the alkali metal hydride is lithium aluminum hydride.

4. The process of claim 1 wherein the contacting agent is an alkali metal hydride.

5. The process of claim 4 wherein the contacting agent is potassium hydride.

6. The process of claim 1 wherein the contacting is performed at a temperature in the range of from C. to 350 C.

7. The process of claim 3 wherein the contacting is performed at a temperature in the range of from 100 C. to 350 C.

8. The process of claim 5 wherein the contacting is performed at a temperature in the range of from 100 C. to 350 C.

9. The process of claim 2 wherein the polyphenyl thioether is represented by the formula:

where m is a whole number from 0 to 6.

10. The process of claim 7 wherein the polyphenyl thioether is m-bis(phenylmercapto)benzene.

11. The process of claim 8 wherein the polyphenyl thioether is m-bis(phenylmercapto)benzene.

12. The process of claim 1 wherein the polyphenyl thioether is a mixture comprising from about 20 to 200 parts by weight of a member of the group consisting of (l) a compound represented by the formula wherein R is a phenyl group, R is a phenylene group and Y and Y are each selected from the group consisting of oxygen and sulfur provided at least one of Y and Y is sulfur and c is a whole number from 1 to 5 and (2) mixtures of (1).

14. A process of claim 1 wherein the polyphenyl thioether is a mixture comprising, by weight, from about 42% to about 99% m-bis(phenylmercapto)benzene and from about 17% to about 58% of a mixture comprising, by weight, from about 20% to about bis(m-phenylmercaptophenyl)sulfide, from about to about 3-phenoxy 3 phenylmercaptodiphenyl sulfide and from about 20% to about 30% bis(m-phenoxyphenyl)sulfide, the contacting agent is potassium hydride and the temperature is in the range of from about C. to about 350 C.

References Cited UNITED STATES PATENTS 5/1967 Campbell et a1. 260-609 XR 2/1969 Campbell 260-609 US. Cl. X.R. 

